Charity worker Rebecca and Alex were expecting their second child - a little girl - in time for Christmas.

The charity worker and her unborn baby were tragically killed on the busy M4 (Image: Western Mail)

Their two-year-old son Cian was seriously hurt in the crash on Tuesday and is still recovering in hospital.

Her shattered colleagues at the homeless charity where she worked paid tribute to Rebecca, credited with helping countless vulnerable young people through her work.

Heartbroken Alex, 28, worked alongside his wife at Shelter Cymru and they were on their way to work when the tragedy happened.

Rebecca's two-year-old son Cian was seriously injured in the smash and is recovering in hospital

Shelter Cymru head of campaigns, Michelle Wales, said: "This is such a tragedy and obviously something we didn't expect.

"She was such a lovely, lovely person and we are all so upset. Staff and trustees are in a state of shock.

"Rebecca had been working for Shelter Cymru for five years building the education and youth information service which has helped thousands of young people to understand the practical steps young people need to take to live independently.

"Without her passion and commitment to young people many would have faced homelessness and uncertain futures.

"Under Rebecca's leadership the education and youth work of Shelter Cymru had become highly regarded by schools, government and other organisations in the field and had made real impacts on the understanding of homelessness and housing need among young people.

"Her colleagues are utterly devastated and all our thoughts are with her partner Alex Evans, our communications officer and their son Cian, both of whom survived the accident."

The couple, of Bridgend, were driving to Swansea when their car crashed on the M4 near Margam, at 8.20am.

A spokeswoman for South Wales Police said: "South Wales Police is continuing to investigate a fatal road traffic collision which happened near the junction of Margam on the M4.

"The collision, involving a BMW, Peugeot and Audi, took place on the westbound carriageway at around 8.20am.

"Mrs Evans's unborn daughter was also tragically killed in the collision. A two-year-old boy was also taken to hospital where he remains.

"A 50-year-old man, who was arrested at the scene, has been bailed pending further enquiries.

"South Wales Police is appealing for any witnesses to the collision to contact them on 101 or anonymously via Crimestoppers on 0800 555 111, quoting reference 1600461041."